Rotary melting furnace with peripheral cooling means



May 5, 1970 FQEX ETAL 3,510,115

ROTARY MELTING FURNACE WITH PERIPHERAL COOLING MEANS Fil ed Feb. 2, 19682 Sheets-Sheet 1 F I INVENTOR HE/ A BMW/7mm RIBCMT 1161/7/75 MM: F051;24w? meoz/r/ou/l/ BY (v at/6 4466 ATTORNEYS M. FOEX ETAL May 5, 1970ROTARY MEL'I'ING FURNACE WITH PERIPHERAL COOLING MEANS 2 Sheets-Sheet 2Filed Feb. 2. 1968 QNQE INVENTOR 175V!!! W W/44m; Awe-:7 2507 MMC F225?"ATTORNEY United States Patent Int. Cl. li27b 7/08 US. Cl. 26333 ClaimsABSTRACT OF THE DISCLOSURE A rotary melting furnace comprising a rotarycylindrical shell having a horizontal axis and two conical extremitiespierced by axial openings, a stationary casing which surrounds saidshell, systems for cooling said shell by means of a cooling fluid andmeans for driving said shell in rotation. The cooling systems comprisespray tubes disposed around the periphery of the shell in axiallyparallel relation thereto and tube sections which terminate at theconical extremities of the shell, the liquid which has served to coolthe conical extremities of the shell being recovered by centrifugationand caused to run over the cylindrical portion of the shell.

The present invention relates to a rotary melting furnace fitted withrotation and cooling systems designed to obviate any further need forflexible seals, the coefficients of friction of which give rise toconsiderable losses of mechanical power While also limiting theproduction capacity of the furnace. The systems under consideration donot set any limitation either on the capacity or the dimensions of thefurnace and accordingly permit the construction of rotary furnaces on anindustrial scale.

In point of fact, in rotary furnaces which are heated by thermal sourcesto high temperatures (solar heat, plasma torches or any otherhigh-temperature heat generator), the charge of material to be meltedand/or partially sintered fills a metallic vessel of circular sectionprovided with a jacket in which a consequent stream of cooling water orany suitable cooling liquid is circulated.

In furnaces of this type, the thermal flux penetrates into a centralcylindrical cavity of small diameter which is formed along therefractory material and begins to melt this latter at the surface assoon as the melting temperature is reached. The need to obtain hightemperatures (of the order of 3000 C.) within the material and evenhigher temperatures within the heat sources entails a very high thermalflux. In order that the metal jacket or casing which contains the chargeof refractory material to be melted should be protected from the meltingprocess, two solutions are contemplated.

In the first solution, provision can be made for an annular thickness ofcharge which is such that the temperature of the non-cooled metallicwall is maintained in the vicinity of 80 to 100 C., thereby making itpossible to operate the furnace without disturbing the human or materialenvironment. But in this case, this annular thick ness would varyaccording to the thermal conductivity of the material to be melted sincethe value of this latter at high temperature can fluctuate within aratio of 3 to 4:1 in the case of refractory oxides. In addition tosubstantial thicknesses of refractory materials, it would therefore benecessary to employ metallic cylinders having a diameter which Wouldcorrespond to the nature of the material to be melted. These two addeddifficulties there- Too fore preclude the use of this system which is oflimited practical interest.

On the other hand, the second solution which consists in cooling bycirculation of water or any other suitable coolant the cylindrical metaljacket or casing which contains the charge of refractory material to bemelted permits the use of a single metallic shell having a fixeddiameter. However, said shell must rotate at relatively high speeds (250to 500 revolutions per minute) in order that the molten material shouldbe retained under the action of centrifugal force on the wall which isstill in the solid state and which is in turn caused to melt by saidmaterial. But in this case, at such angular velocities, the linearvelocities of the metallic shell increase considerably with its radius,that is to say with the quantity of molten materials produced by therotary furnace.

However, the liquid coolant contained within a rotating metal jacket ofthis type must be admitted into the double wall which constitutes saidjacket, then be discharged therefrom through stationary supply tubesections which are placed at its periphery and connected by means offlexible seals. An arrangement of this kind results in substantialfriction which increases with the diameter of the furnace and thereforewith its production capacity. The friction referred to becomes not onlya source of considerable loss of mechanical power for driving thefurnace in rotation but also sets a limitation on any increase inproduction capacity on an industrial scale, as could readily becalculated from the angular velocities mentioned above and with thecoefficient of friction of known seals.

The present invention makes it possible to overcome this loss of powerand especially the limitation which would be imposed on the volume ofproduction of this type of furnace. In fact, the rotation and coolingsystems with which the furnace according to the invention is equippedmake it possible to dispense with flexible seals.

More specifically the rotary melting furnace according to the presentinvention which comprises a rotary cylindrical shell having a horizontalaxis and two conical extremities pierced by axial openings, a stationarycasing which surrounds said shell, systems for cooling said shell bymeans of a cooling fluid and mean for driving said shell in rotation, ischaracterized in that said cooling sys tems comprise at least oneannular zone which is concentric with the moving shell, said annularzone being connected to a pipe for the admission of the cooling fluidand adapted to communicate on the one hand with spray tubes disposedaround the periphery of the shell in axially parallel relation theretoand on the other hand with tube sections which terminate at the conicalextremities of the shell, the liquid which has served to cool saidconical ex tremities of the shell being recovered by centrifugation andcaused to run over the cylindrical portion of the shell.

Further properties and advantages of the present invention will becomeapparent from the following description of one embodiment of saidfurnace which is given by way of explanation but not in any sense by wayof limitation,

reference being made to the accompanying drawings, in

which:

FIG. 1 illustrates the melting furnace in accordance with the invention;

FIG. 2a illustrates the furnace together with its fixing assembly;

FIG. 2b is a top view of the furnace which is equipped with four plasmatorches.

The furnace in accordance with the invention as shown in detail in FIG.1 comprises a moving unitary casing 1 which has the shape of ahorizontal cylinder, an axis of rotation 00' and two conicalextremities. There are formed at the center of said extremities circularopenings 2 and 3 which are employed for the purpose of heating thefurnace and pouring molten refractory materials which may also berefined. A second stationary casing 4 surrounds the moving portion 1.The movement of rotation of said moving portion about the axis withrespect to said stationary casing is carried out by means of twoball-bearings 5 and 6 which are disposed at each extremity of thecylinder.

The cooling fluid (such as water, for example) is admitted at the top ofthe stationary casing 4 through tubes such as the tube 7 which feed twoannular zones 8 and 9. Said zones serve to distribute the cooling fluidon the one hand to spray tubes 10 which are disposed around theperiphery of the moving casing and parallel to its axis and, on theother hand, to short tubes 11 which open onto the terminal conicalportions of the cylinder.

At the axial center of the furnace, there is located a free zone 12 inwhich the plasma is heated (primarily by radiation) and which isfollowed in the direction of the casing 1, first by a fusion zone 13,then by a gradual and decreasing-sintering zone 14.

The moving casing 1 is driven in rotation about the axis 00' by means ofa gear system consisting of a pinion 15 (the driving means having beenomitted from the figure) and a ring gear 16 which is rigidly fixed tothe casing 1.

The cooling liquid is discharged at the base of the apparatus through anopening 17.

The cylindrical portion of the furnace is powerfully cooled by means ofthe spray tubes 10, then by the cooling liquid which is caused to flowupwards by centrifugation from the terminal conical portions, then runsover the metallic cylinder 1.

The cooling liquid which serves to cool the terminal conical zones bymeans of the short tubes 11 flows up under centrifugal action withoutany need to provide seals at 18 which would absorb a substantial amountof mechanical energy. Cylindrical assemblies such as 19 for the rotatingportion of the furnace and cylindrical assemblies such as 20 for thecooling spray tubes make it possible to increase the length of thefurnace if necessary and therefore to increase its production capacity.

In FIG. 2a, the furnace which is illustrated diagrammatically at 21 ismounted in clamping collars 22. The furnace is balanced by means of acounterpoise 23 constituted by the motor set from which the furnace isdriven in rotation. The complete assembly is fixed on a column 24 whichpermits of azimuthal position-setting. The column is in turn fixed on aconventional frame 25 which permits of positional adjustment.

In the case of heating of the furnace by means of plasma torches 26,FIG. 2b shows the arrangement which can be adopted for said torches.

It will be understood that the present invention has been described inthe foregoing by way of explanation but not in any limiting sense andthat any detail modifications can be contemplated without therebydeparting either from the scope or the spirit of the invention.

What we claim is:

1. A rotary melting furnace comprising a rotary cylindrical shell havinga horizontal axis and two conical extremities pierced by axial openings,two outer members secured to said conical extremities defining two outerchambers, a stationary casing which surrounds said shell, systems forcooling said shell by means of a cooling fluid and means for drivingsaid shell in rotation, characterized in that said cooling systems arestationary and comprise at least one annular zone which is concentricwith the moving shell, said annular zone including a plurality of pipesfor the admission of the cooling fluid to a plurality of spray tubesdisposed around the periphery of the shell in axially parallel relationthereto and to a plurality of peripheral tube sections within said outerchambers which open at the conical extremities of the shell, the liquidwhich has served to cool said conical extremities of the shell adaptedto be recovered by centrifugation through said outer chambers and causedto run over the cylindrical portion of the shell, and meanscommunicating with the lower part of said zone to discharge said liquid.

2. A rotary melting furnace in accordance with claim 1, characterized inthat the rotary cylindrical shell and the spray tubes consist of, at oneof the extremities thereof, replaceable pieces whereby the productioncapacity of the furnace may be varied.

3. A rotary melting furnace in accordance with claim 1, characterized inthat the moving shell is rotatably mounted inside the stationary casingon ball-bearing raceways.

4. A rotary melting furnace in accordance with claim 1, characterized inthat the means for driving the shell in rotation comprise a drivingpinion which is adapted to cooperate with a ring gear which is rigidlyfixed to said shell.

5. A rotary melting furnace in accordance with claim 1, characterized inthat said furnace is mounted in clamp ing collars and balanced by acounterpoise on a fixing column which permits of positional adjustmentof said furnace.

References Cited UNITED STATES PATENTS 644,926 3/1900 Kelling et a1.164297 X 939,817 11/1909 Edison. 3,257,196 6/1966 Foex 266-33 X FOREIGNPATENTS 182,488 7/1955 Austria. 8,768 2/ 1957 Germany.

ROBERT D. BALDWIN, Primary Examiner U.S. Cl. X.R.

